New
New
Year 11
AQA
Higher

Orbital motion of artificial satellites: relationship between radius and speed

I can describe changes to a satellite’s speed and velocity and explain what happens to its orbital radius if its speed changes.

New
New
Year 11
AQA
Higher

Orbital motion of artificial satellites: relationship between radius and speed

I can describe changes to a satellite’s speed and velocity and explain what happens to its orbital radius if its speed changes.

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Lesson details

Key learning points

  1. Artificial satellites orbit Earth because of the gravitational attraction between them.
  2. The speed of a satellite along its orbit around Earth is constant.
  3. The velocity of a satellite along its orbit around Earth constantly changes as it changes direction.
  4. The centripetal force on a satellite makes it accelerate and change direction, but not speed.
  5. To orbit in a stable orbit, the orbital radius of a satellite must change if its speed changes.

Keywords

  • Satellite - an object which orbits a planet; satellites can be natural (moons) or artificial

  • Polar orbit - an orbit in which the satellite passes over the poles of a planet

  • Geostationary orbit - an orbit in which the satellite is stationary in the sky as it orbits in the same time as the planet, directly above its equator

  • Orbital path - the path a satellite takes around the planet it orbits

  • Orbital radius - the radius of an orbit, measured from the centre of a planet

Common misconception

Motion is always in the direction of the force acting on an object.

Provide pupils with opportunity to experience a radial force changing the direction of a small object in order to make it move in a circular path.

Demonstrate (with care) the effect of a radial force by releasing a string that is forcing a small object to move in a circular path. The object will continue to move in a straight line in the direction it was travelling when the force is removed.
Teacher tip

Equipment

Thin plastic tubes (e.g. shells of ballpoint pens), rubber bung, strong thread, masses and mass holder.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
What happens when the Earth orbits the Sun?
the Earth spins on its axis so it faces the Sun once each day
Correct answer: the Earth moves in a circular path around the Sun once each year
the Sun moves in a circular path around Earth once each day
the Sun moves in a circular path around Earth once each year
Q2.
Which of the following objects orbit Earth?
Correct answer: the Moon
the Sun
stars
Correct answer: the International Space Station
Q3.
Which of the following objects orbit only the Sun?
Correct answer: asteroids
Correct answer: dwarf planets
stars
the moons of Jupiter
Q4.
Starting with the planet with the fewest moons, sort the following planets into increasing order of number of moons.
1 - Mercury
2 - Earth
3 - Mars
4 - Jupiter
Q5.
How many artificial satellites orbit Earth?
fewer than ten
about a hundred
about a thousand
Correct answer: more than ten thousand
Q6.
Starting with the planet that takes the shortest amount of time, sort the following planets into increasing order of how long they take to orbit the Sun.
1 - Mercury
2 - Venus
3 - Earth
4 - Mars
5 - Jupiter
6 - Saturn

6 Questions

Q1.
Titan is a large moon of Saturn. Which of the following statements most accurately describes Titan?
Titan is a natural satellite of the Sun.
Correct answer: Titan is a natural satellite of Saturn.
Titan is an artificial satellite of Saturn.
Titan is a planet in orbit around Saturn.
Q2.
Which of the following types of satellites are often found in low Earth orbits?
the Moon
communication satellites
Correct answer: observation satellites
Q3.
Why are communication satellites usually placed in a circular orbit of 35 785 km above the Equator?
so they don't collide with the Moon
Correct answer: so they remain above one point on Earth's surface
so they move across the whole of Earth each day
so they can send signals directly to every country on Earth
Q4.
What force acts on a satellite in geostationary orbit?
frictional force
Correct answer: gravitational force
thrust
buoyancy
Q5.
Starting with the satellite that has the fastest orbit, sort the following satellites of Earth into increasing order of how long they take to orbit Earth.
1 - a weather satellite in a low Earth orbit
2 - a communications satellite in a geostationary orbit
3 - the Moon
Q6.
A satellite in low Earth orbit has an orbital radius of 8000 km and is travelling at a speed of 25 000 km/h. How many times does it orbit Earth in 24 hours?
Correct Answer: 12, 11.9, 11.94, 11.937

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